The present invention relates to an improved apparatus for mounting jet propulsion engines on an airfoil and to a unique means for intercepting a portion of the engine generated exhaust effluent and channeling such effluent into boundary layer control supply plenums in the airfoil.
It is preferable in both commercial and military craft of the passenger or transport type to employ a midwing or low wing configuration, especially in larger aircraft, to provide structural integrity and to provide ease of access to the wing structure for refueling and maintenance. High bypass turbofan jet propulsion engines are desirably employed in such aircraft because of their relatively high thrust-to-weight and low sound level characteristics. Problems arise in mounting such turbofan engines on midwing and low wing configured aircraft because among other reasons of the relatively large diameter of such engines as compared to straight turbojet engines.
Most prior art midwing and low wing aircraft employ pod-mounted engines, i.e., engines that are mounted on struts that extend downwardly from the wing to a location below the wing. When used with midwing and low wing aircraft, pod-mounted turbofan engines do not provide adequate ground clearance under certain operating conditions and also tend to ingest foreign objects upon landing and takeoff. Moreover, prior art engine mounting struts must be relatively heavy and must be reinforced to withstand not only the normal forward thrust components but also the reverse thrust components created by thrust reversal for aircraft braking purposes upon landing. In addition, the cowl structure of pod-mounted turbofan engines must be constructed to incorporate and house the thrust reversing mechanism and to withstand the thrust loads when the reversers are in operation.
There is also a trend toward utilization of boundary layer control systems on the wings of aircraft designed to take off and land in relatively short distances. Boundary layer control systems normally employ engine exhaust effluent as the source of control fluid, which is supplied from plenums in the wing structure to slots running spanwise along the wing structure adjacent the leading edge. The exhaust effluent is fed across the surface of the wing to maintain better attachment of the ambient air stream flowing across the wing to enhance aerodynamic lift. When pod-mounted turbofan engines are utilized, the engine exhaust effluent must be channeled from the engine, up through the mounting strut, and into the boundary layer control fluid supply ducts in the wings. This additional structural requirement adds both weight and bulk, and consequently additional drag, to the aircraft.
When turbofan engines are pod-mounted on low wing and midwing aircraft, relatively long and complex retractable landing gear are required to provide sufficient ground clearance for the engines. Not only are such landing gear undesirable from the standpoint of maintenance and operation, they also add weight and additional drag to the aircraft. Moreover, long landing gear places the aircraft profile a significant distance above the ground, necessitating special loading and unloading platforms. This problem is especially significant in larger aircraft having two or more vertically spaced, deck levels.
As can be understood from the foregoing explanation, a turbofan engine mounting configuration other than conventional pod-mounting is needed for low and midwing aircraft designs. Accordingly, objects of the present invention are to provide a lightweight, low drag, engine installation for an aircraft; to provide an engine installation that allows the use of relatively short landing gear on a low or midwing aircraft; to provide an engine installation that is easily accessible for maintenance; to provide an engine mounting structure that allows the engine to be easily removed from an aircraft for major repair and replacement; to provide a turbofan jet propulsion engine installation requiring a minimum of ducting and control mechanism for supplying fan air effluent to a boundary layer control system; to provide a turbofan jet propulsion engine with boundary layer control fluid inlet ducts that are designed integrally with the engine mounting structure; to provide a means for controlling the flow of fan effluent through such boundary layer control fluid inlet ducts; to provide a means for preventing blowback of control fluid and loss of control fluid pressure through the inlet ducts; to provide a turbofan jet propulsion engine installation in which the turbine and engine cowl or nacelle are integrated with support structure, which in turn is removably mounted directly onto the airfoil; to provide such an engine installation with mounting structure having four attachment points for removably affixing a turbofan jet propulsion engine to an airfoil, and particularly to a wing; and to provide mounting structure for a turbofan jet propulsion engine wherein the engine is cantilevered forwardly of the wing and is bisected by the major chordal plane of the wing; and to provide means in such mounting structure for effectively and efficiently splitting the fan and turbine effluent into two streams and directing each of these streams on opposing sides of the airfoil on which the engine is mounted.